Galvanic detection of oxygen in a spinning cell steam chamber

ABSTRACT

IN AN APPARATUS FOR SPINNING SYNTHETIC FILAMENTS OF THE TYPE THAT INCLUDES AN EXTRUSION DEVICE FROM WHICH FILAMENTS PASS SUCCESSIVELY THROUGH A STEAM CHAMBER AND A QUENCHING CHAMBER TO A WINDUP, A MEANS IS PROVIDED FOR CONTINUOUSLY DETECTING AND INDICATING THE AMOUNT OF OXYGEN IN THE STEAM CHAMBER IN THE RANGE OF CONCENTRATIONS OF FROM 0.01 TO 1.0% AT TEMPERATURES THAT RANGE FROM 100 TO 350*C. THE DETECTING MEANS IS A GALVANIC CELL IN COMMUNICATION WITH THE STEAM CHAMBER AND CONNECTED TO AN INDICATOR. THE CELL INCLUDES A POROUS GRAPHITE CUP CONTAINING AN ELECTROLYTE MIXTURE AND A MOLYBDENUM ANODE CENTRALLY LOCATED IN THE CUP.

June 27, 1972 c. RAPISARDA 3,672,800

GALVANIC DETECTION OF OXYGEN IN A SPINNING CELL STEAM CHAMBER Filed July 1, 1970 FIG.!

2 Sheets-Sheet 1 INVENTOR CARIELO RAPISARDA ATTORNEY C. RAPISARDA June 27, 1972 GALVANIC DETECTION OF OXYGEN IN A SPINNING CELL STEAM CHAMBER Filed July 1, 1970 2 Sheets-Sheet: 2

RA OD TR A ms N 0 0 R 6 0 L E l I R U l A c N I y (I E o aJ 5 ll 1 0 N T A 0 L A 5 L R O E S c 6 w. C S. M M r 1| 7J V 0.... .LW A A N GIL E I M N x 0 IILLIVOLTS ATTORNEY United States Patent Olfice 3,672,800 Patented June 27, 1972 Int. Cl. Dllld 13/02 US. Cl. 425-71 2 Claims ABSTRACT OF THE DISCLOSURE In an apparatus for spinning synthetic filaments of the type that includes an extrusion device from which filaments pass successively through a steam chamber and a quenching chamber to a windup, a means is provided for continuously detecting and indicating the amount of oxygen in the steam chamber in the range of concentrations of from 0.01 to 1.0% at temperatures that range from 100 to 350 C. The detecting means is a galvanic cell in communication with the steam chamber and connected to an indicator. The cell includes a porous graphite cup containing an electrolyte mixture and a molybdenum anode centrally located in the cup.

BACKGROUND OF THE INVENTION This invention relates to the manufacture of synthetic fibers and, more particularly, to monitoring the oxygen content of the atmosphere into which the spun fiber is initially extruded.

One of the important goals in the melt spinning art has been to effect longer periods of spinning without interruption for removal and cleaning of spinnerets. One problem affecting spinneret life arises because the organic materials being spun occasionally leave a small carbonized deposit at the spinning orifice which tends to block the orifice and accumulate polymer. If unattended, these accumulations may be of size to deflect the filament being extruded, to slow down the extrusion or even hold back the extrusion until a mass of polymer drips from the orifice. The accepted method to correct this condition is to wipe the face of the spinneret with a brass stick to cleanse the surface at predetermined intervals. It has also been established that the frequency for wiping yarns spun from some polycarbonamides is critically related tooxygen concentration at the spinneret face, thus dictating the need for reliable detection and monitoring the oxygen content of the atmosphere near the spinneret during melt spinning. However, the art has apparently failed to recognize the importance of such monitoring or if the art did recognize the importance, a suitable apparatus was not developed. The present invention fulfills this need.

SUMMARY OF THE INVENTION In a melt spinning apparatus of the type that includes an extrusion device from which filaments pass successively through a steam chamber and a quenching chamber to a collecting means there is provided a means for detecting the oxygen content of the atmosphere adjacent the extrusion device in the steam chamber. This detecting means includes a galvanic cell in communication with and for detecting oxygen in the steam chamber, the cell generates a voltage proportional to oxygen in the chamber. The cell comprises a porous graphite cathode cup containing an electrolyte mixture in parts by weight of 16 parts sodium hydroxide, 8 parts potassium hydroxide, 20 parts magnesium oxide and 1 part molybdenum sesquioxide and a molybdenum anode centrally located in the cup. Means are provided for indicating the voltage generated by the cell corresponding to oxygen content of the steam chamber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of a melt spinning apparatus fitted with the oxygen detecting device of this invention.

FIG. 2 is a sectioned-schematic illustration of the galvanic cell shown coupled to the steam chamber in FIG. 1.

FIG. 3 is a schematic circuit diagram of the means for indicating galvanic cell voltage.

FIG. 4 is a graph showing the relationship between cell voltage and oxygen concentration at 300 C. as determined during test runs.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring now to FIG. 1, molten polymer from a source (not shown) is supplied to metering gear pump 10 which forces the polymer at a constant rate through spinning pack 12 and out spinneret 14 as filaments 16. The filaments pass successively through a steam chamber 18, a quenching chamber 20, over rotating roller 22 and through traverse guide 24 to package 26.

An oxygen sensitive galvanic cell 30 is attached to and extends through the wall of steam chamber 18 and is aligned horizontally between two rows of orifices in spinneret 14. The cell, as will be described later, detects the amount of oxygen in steam chamber 18 by generating a voltage proportional thereto which, in turn, is fed over lines 32, 34 to indicator 36.

As best shown in FIG. 2, cell 30 includes a porous graphite cup 31 containing an electrolyte 35 and a centrally located molybdenum anode 3-7. The anode is insulated from the cathode by fused stabilized zirconia sections 3-9 and the open end of the cell is closed by cap 33. The preferred electrolyte mixture contains an anode oxide and includes in parts by Weight 16 parts sodium hydroxide, 8 parts potassium hydroxide, 20 parts magnesium oxide and 1 part molybdenum sesquioxide. These were ground then wetted with distilled water to make a heavy paste which is placed in the cup after the anode 37 has been positioned.

.A bucking voltage is applied to cell 30 in order to keep null current conditions and to prevent an unsteady state condition due to anode corrosion and polarization. FIG. 3 shows the voltage being applied from a variable source 40 with switches 42, 44 closed. The level of voltage from source 40 is such that a zero reading is obtained on voltmeter 46. Source 40 voltage readings may be obtained by opening switch 44 after adjusting 40 to obtain a null reading on voltmeter 46 with 42 and 44 closed. Alternatively, a conventional potentiometer may be used to measure the null-current voltage of cell 36.

In a series of test runs wherein oxygen concentration at 300 C. steam was varied in a controlled manner from 0.01 to 1.0% by volume, the output signal from cell 30 ranged from 468 to 574 millivolts. Reproducibility between excursions with increasing and decreasing oxygen content was excellent. The cell potential was found to be a unique measure of oxygen concentration with the cell voltage at equilibrium being a straight line function of the log of the oxygen concentration at a constant temperature. This confirmed relationship is shown in FIG. 4. The cell was further tested for insensitivity to steam contaminants normally present at the spinneret during spinning such as carbon dioxide, silicone spray and monomer vapors. None of these affected cell response, once the specified temperature was established. The cell sensitivity remained high and substantially constant at temperatures up to 350 C.

It wil lbe readily recognized that the above-described invention which provides a sensitive and direct method for monitoring oxygen at the critical point of extrusion through a spinneret under actual spinning conditions is a valuable contribution to the art of fiber manufacture.

Many difierent embodiments of the invention may be made without departing from the spirit and scope thereof and it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the appended claims.

What is claimed is:

1. In a melt spinning apparatus of the type that includes an extrusion device from which filaments pass successively through a steam chamber and a quenching chamber to a collecting means, the improvement comprising: a galvanic cell in communication with and for detecting oxygen in said steam chamber, said galvanic cell comprising: a porous graphite cathode cup; an electrolyte mix ture contained in said cup comprising a mixture in parts by weight of 16 parts sodium hydroxide, 8 parts potassium hydroxide, 20 parts magnesium oxide and 1 part molybdenum sesquioxide and a molybdenum anode centrally located in said cup, said cell generating a voltage proportional to the oxygen in said steam chamber; and means connected to said cell for indicating the voltage generated by the cell corresponding to oxygen content of the steam chamber.

2. In an apparatus for the production of synthetic filaments including an extrusion device from which filaments pass successively through a steam blanketing chamber and a quenching chamber toa collecting means, the improvement comprising: a galvanic cell in communication with said steam blanketing chamber, said galvanic cell comprising: a porous graphite cathode cup; an electrolyte mixture contained in said cup comprising a mixture in parts by weight of 16 parts sodium hydroxide, 8 parts potassium hydroxide, 20 parts magnesium oxide and 1 part molybdenum sesquioxide; and a molybdenum anode centrally located in said cup; means for supplying a bucking voltage to said cell; and a voltmeter connected to said cell and said bucking voltage supply means.

References Cited J. SPENCER OVERHOLSER, Primary Examiner M. O. SUTTON, Assistant Examiner US. Cl. X.R. 

